This invention pertains generally to the decoding of multi-bit digital signals and more particularly to a decoder and method utilizing logic circuits to effect the desired decoding.
In medium scale integration (MSI) systems, programmable read-only memories (PROM's) are frequently used for decoding binary signals such as the operation codes (OPCODE) of a computer instruction set. In large scale integration (LSI) systems, however, PROM decoders are not satisfactory because they have unused bits which waste valuable chip space. In systems utilizing NMOS and PMOS technology, programmable logic arrays (PLA's) are sometimes used as decoders. Where they can be used, PLA's have the advantage of almost unlimited fan-in capability. However, PLA's are difficult to use with other technologies such as CMOS.